Method of making type drums



Oct. 3, 1961 Filed May 23, 1960 HK/GH VOLTAGE Power? SUPPLY C. A. CHRISTOFF METHOD 0F' MAKING TYPE DRUMS 2 Sheets-Sheet l TroP/vey Oct. 3, 1961 c. A. cHRlsToFF 3,002,452

METHOD 0F MAKING TYPE DRUMS Filed May 25, 1960 2 sheets-sheet 2 ELKE E @Hp/J A (wp/5 mff 3,002,452 METHD 0F MAKING TYPE DRUMS Chris A. Christo, San Gabriel, Calif., assignor to Clary lorporatlon, San Gabriel, Calif., a corporation of Caliorma Filed May 23, 1960, Ser. No. 31,116 8 Claims. (Cl. 101-401.2)

'Ihis inventionprelates to the manufacture of printing type drums and has particular reference to a method of forming type drums or cylinders having a number of circumferentially extending rows of raised type characters spaced thereon.

Heretofore, type wheels capable of extended use have been successfully formed by a knurling process wherein a hardened master wheel having intaglio type characters engraved therein is rotated under relatively lhigh pressure against an unhardened blank wheel thereby forming raised type characters. The latter is thereafter hardened to form a type wheel. -In this procedure, the swagging r knurling process causes the material of the wheel blank surrounding the raised type characters thus formed to flow laterally under pressure toward the sides of the blank.

,The above process is satisfactory in cases where the wheel blank is relatively narrow and wherein only one or two circumferentially extending rows are formed thereon or wherein a drum having a large number of rows of type characters thereon is formed of relatively soft metal such as brass. However, dillculty is encountered in attempt-ing to knurl a large number of rows of raised type characters on a steel or the like drum, even though the latter is unhardened, `because of the excess amount of metal which must be removed by such knurling process from the background extending around the raised characters.

Accordingly, the principal object of the present invention is to facilitate forming a steel or other hard metal type drum having a plurality of rows of raised type characters around the periphery thereof.

Another object -is to reduce the cost of making a type drum of the foregoing type.

A still further object is to accurately form raised type characters of a type drum of the foregoing type- The manner in which the above and other objects of the invention are accomplished will be readily understood in reference to the following specification when read in conjunction with the accompanying drawings, wherein:

PIG. l is an elevational view, partly in section of an apparatus for forming tool drums.

FIG. 2 is an elevational View showing the first step of forming the type cylinder.

FIG. 3 is an elevational view showing the second step of forming the type cylinder.

FIGS. 4 through 8 are enlarged sectional views illustrating the different steps followed to form a type cylinder according to a preferred form of the present invention.

A master drum 11 (FIGS. 1, 4 and 6) is formed of hardened steel having engraved on its outer periphery a plurality of circumferentially extending rows of male type characters 12. The drum 11 also has gears 13 and 14 integrally formed, or attached to, its opposite ends. The pitch diameter of these gears are the same as the diameter of the drum.

The drum 11 is mounted on a shaft 15 rotatably mounted in the inner races of ball bearings -16 and i7, the outer races of said bearing being mounted in support frames 18 and 19.

A 'rst tool drum 211 (FIGS. l and 4) is mounted on a shaft 22, said shaft being rotatably mounted in the inner races of ball bearings 23 and 24. The outer races of 3,002,452 Patented Oct. 3, 1961 said bearings are mounted in a vertically slidable frame 23.

The `drum 21, having a smooth cylindrical surface, is formed of a metal which is relatively soft while also being a good conductor of electricity, such as brass or some similar metal. The latter drum is of the same diameter as the master drum 111. Gears 26 and 27 having the same number of teeth and the same pitch diameter as the gears 13 and 14 of the master drum 111 are either attached to or :formed integrally on the opposite ends of the drum 21.

A motor 2 8 is provided which, through a speed reduction gear box 29, drives the shaft 15.l The latter rotates the drum 1l.

The slide frame 25 is positioned in slots 31 and 32 of the respective supports 1-8 and -19 to thereby mesh the gears 26 and 27 of the drum 21 with the respective gears i3 and i4 of the drum 11 so that as the drum 11 is rotated by the motor 23 it will, in turn, rotate the drum 21 in the opposite direction and at the same peripheral speed. Suitable means (not shown) is provided for moving the frame 25, and therefore the drum 121, toward the drum 11 so that as the drums rotate, the male type characters of the master drum will be impressed into the soft metal of the tool drum 21 as shown in FIG. 4, thereby leaving the drum 21 with circumferentially extending rows of female type characters 33.

When the tool drum 21 is finished, it is mounted on a shaft 3d rotatably supported in supports Iltfia and 19a (FIG. 2) which are similar to supports 18 and 19, and similar means comprising a motor 28a and a speed reducing gear box 29a are used to drive the shaft 34.

A type cylinder or drum 35 in its blank stage, i.e., with a smooth cylindrical periphery, is mounted on a shaft 36, said shaft being rotatably mounted in a slidable frame 25a. The type drum is the same diameter as the drums 11 and 21. The opposite ends of the drum 35 have gears 37 and 38, attached to or integrally formed thereon, said gears having the same number of teeth and the same pitch diameter as the gears 26 and 27.

The drum 35 and a portion of the drum 21 are submerged in a container 39 containing an oil el having dielectric properties.

The shaft 36, carrying the drum 35 projects through the side of the container 39 and through suitable fluid seals di?. The shaft is in wiping engagement with a brush 42 representing the positive side of a high voltage, rapidly nterrupted, direct current power supply 43, while the shaft 34 carrying the drum 21 is in wiping engagement with a brush 44 representing the negative side of the power supply 43.

The operation performed on the drum 35 is to erode away by electrical discharge, the metal at specific areas so as to leave equally spaced protruding rows (FIG. 5) of type characters on the type cylinder 35. The eroding is brought about by the high Voltage power supply 43 building up a high voltage potential between the drum 2 and the drum 35 during each discharge cycle. As thel will become more and more attracted to the drum 35 those portions of the drum 35 which are nearest adjacent points on the drum 21 will be eroded faster.

By rotating the drums 21 and 35 and at the same time moving the drum 35 closer to the drum 21, through means not shown, removal of metal from the former is continuous and the resulting raised characters 45 formed on the drum 35 approximate, in a reverse sense, the intaglio characters of the drum 21 `as shown in FIG. 5.

As rotation of the drums 21 and 35 and electrical discharge between the .two continue, the type characters 45 on the drum 35 are formed. However, during such process, the surface of the drum 21 becomes slightly eroded due to the fact that some of the particles forming the metallic vapor have suflicient momentum to pass through the dielectric oil and strike the surface of the drum 21. Thus, the `shape of the surface of drum 21 changes somewhat and, accordingly, the resulting type characters 45 on the cylinder 35 are not perfect replicas of the type characters 12 on the drum 11. This will hold true, to a lesser extent, even though the process is continued using a second duplicate matrix 21.

The next step is to form a second tool drum 47 (FIG. 6) which is formed in the same manner as the first tool drum 21 as aforedescribed and illustrated in FIGS. l and 4, the only `change being that instead of the drum being made of brass or some similar metal, the second tool drum 47 is formed of soft steel with the intaglio characters rolled or knurled therein. Such knurling process does not involve extremely high pressures since the total area of the raised characters, representing the area of the metal to be displaced, is relatively small compared to the remaining area of the drum.

After the second tool drum 47 is hardened, it is placed in a slidable frame Zb (FIG. 3) in contact with the type cylinder 35 which has been placed in support frames 18b and 19b. Gears 50 and 51 on the drum 47 are meshed with the gears 37 and 38, respectively on the drum 35 and care is taken to insure that the intaglio characters on the drum 47 mesh or align with the corresponding raised characters on the drum 35. The rolling of the drums is done in the same manner as aforedescribed in connection with FIG. l by a motor 28b, speed reducing gear box ZSb and a shaft b carrying the type drum 35 (FIG. 3). The second tool drum 47 is now pressed against the type cylinder 35, through means not shown, so that the fem-ale characters of the tool drum will press on to the male characters 45 on the type cylinder to nally finish or knurl the same thus correcting any minor irregularities which may exist so that the finished characters are exact duplicates of the type characters on the master drum 11.

After the drums have been rolled together, thereby leaving the type characters on the type cylinder in their finished state, the cylinder is hardened leaving a finished product as shown in FIG. 8.

As can be seen by FIGS. 5 and 7, the final knurling operation involves forming of the approximated type characters 45 and since the majority of back ground metal has been removed by erosion there Will be no extremely high rolling pressures involved which might otherwise result in distortion of the drum during the rolling operation.

Although the foregoing process of electrically eroding the surface of the type cylinder could be continued by substituting additional new tool drums, i.e., 21, until at least substantially perfect type characters are formed on the cylinder 35, such additional operation would be unduly costly and time consuming.

Also, the above noted process of electrically eroding the surface of the type cylinder could be utilized to concurrently form or at least finish the gears 37 and 38 on the type cylinder.

Although the invention is described in detail and therefore certain specific terms and languages are used herein, it is to be understood that the present disclosure is illustrative rather than restrictive `and that changes and modifcations may be made without departing from the spirit or scope of the invention as set forth in the claims appended hereto.

Having thus described the invention, what I desire to be secured =by United States Letters Patent is:

1. The method of forming type drums which comprises making a relatively hard metal master drum having raised characters thereon, rotating said master drum against a first relatively soft metal tool drum to form intaglio characters in said tool drum, rotating said tool drum and a type cylinder adjacent each other While effecting an elec tric discharge across said tool drum and said type cylinder in a direction to form raised type characters on said type cylinder, rotating said master drum against a second relatively soft metal tool drum to form intaglio characters in said second tool drum, hardening said second tool drum, and subsequently rotating said second tool drum against said type cylinder.

2. The method of forming type drums which comprises making a rel-atively hard metal master drum having raised characters thereon, rotating said master drum against a relatively soft tool drum to form intaglio characters in said tool drum, rotating said tool drum and a type cylinder adjacent each other While effecting an electric discharge across said tool drum and said type cylinder in a direction to form raised type characters on said type cylinder, rotating said master drum against a second relatively soft metal tool drum to form intaglio characters in said second tool drum, subsequently rotating said second tool drum against said type cylinder to finish said type characters thereon, and thereafter hardening said type cylinder.

3. The method of forming type drums which comprises making a relatively hard master drum having raised characters thereon, rotating said master drum against a first relatively soft metal tool drum to form intaglio characters in said tool drum, rotating said tool drum and a blank type cylinder adjacent each other in opposite directions and at the same peripheral speed while effecting an electric discharge across said tool drum and said type cylinder in a direction to form raised characters on said type cylinder, rotating said master drum against a second relatively soft metal tool drum to form intaglio characters in said second tool drum, hardening said second tool drum, and subsequently rotating said second tool drum against said type cylinder to cause said raised characters on said type cylinder to engage corresponding intaglio characters on said second tool drum whereby to finally form said last mentioned characters.

4. The method of forming type drums which comprises rolling a hardened master drum having raised characters thereon against a first relatively soft metal tool drum to form intaglio characters in said tool drum, rotating said tool drum and a blank type cylinder adjacent each other in opposite directions and lat the same peripheral speed while causing an electric discharge across said tool drum and said type cylinder in a direction to form raised type char-acters on said type cylinder approximating said first mentioned raised characters, rotating said master drum against a second relatively soft metal tool drum to form intaglio type characters in said second tool drum, hardening said second tool drum, and subsequently rotating said second tool drum against said type cylinder to finally form said type characters.

5. The method of forming type drums which comprises making a first relatively soft metal tool drum having intaglio characters therein, making a second relatively soft metal tool drum having intaglio characters therein which duplicate said first mentioned characters, rotating said first tool drum adjacent a blank type cylinder While effecting an electric discharge across said first tool drum and said type cylinder in a direction to form raised characters on said type cylinder, hardening said second tool drum, and subsequently rotating said second tool drum against said type cylinder to finally form said raised type characters of said type cylinder.

6. The method of forming type drums which comprises making a relatively hard metal master drum having raised characters thereon, rotating said master drum against a rst relatively soft metal tool drum to form intaglio characters in said tool drum, rotating said tool drum and a type cylinder in spaced parallel relation and at the same peripheral speed, causing an electrical discharge across said tool drum and said type cylinder in a direction to cause emission of molecules from the surface of said type cylinder whereby to erode the portions of the surface of said type cylinder nearest adjacent portions of said tool drum to form raised type characters on said type cylinder, rotating said master drum against a second relatively soft metal tool drum to form intaglio characters on said second tool drum, hardening said second tool drum, and subsequently rotating said second tool drum against said type cylinder to finally form said raised type characters 0n said type cylinder.

7. The method of forming type drums which comprises making a relatively hard master drum having raised characters thereon, rotating said master drum against a rst relatively soft metal tool drum to form intaglio characters in said tool drum, rotating said tool drum and a type cylinder in spaced parallel relation and at the same peripheral speed, and causing an electrical discharge across said tool drum and said cylinder in a direction to cause emission of molecules from the surface of said type cylinder whereby to erode the portions of the surface of the type cylinder nearest adjacent portions of said tool drum to form raised type characters on said type cylinder.

8. The method of forming type drums which comprises making a rst tool drum having intaglio characters therein and a gear coaxial with said drum, said gear having -a pitch diameter equal to the diameter of said drum, rotating said tool drum and a type cylinder in spaced parallel relation and at the same peripheral speed, causing an electrical discharge across said tool drum and said type cylinder in a direction to cause emission of molecules from the surface of said type cylinder whereby to erode the portions of the surface of said type cylinder nearest adjacent portions of said tool drum to form raised type characters and a gear on said type cylinder.

No references cited. 

